In the manufacturing of bevel gears, a burr (also referred to as a primary burr here) can arise, for example, at the outer tooth end due to cutting machining. Because of the high risk of injury, but also because of the risk of complete hardening when hardening the bevel gears, these tooth edges are frequently broken by a chamfer in the scope of chamfering.
In the described chamfering, depending on the constellation, a secondary burr can result on the bevel gear upon removal of the primary burr. If the primary deburring is performed using a deburring tool, the cutting edge(s) of which are guided outward coming from a tooth gap, the secondary burr thus results on the outer circumference of the bevel gear, as shown in FIG. 1A. In contrast, if the deburring tool is guided from the base to the head of the bevel gear 10 (into a tooth gap) during the primary deburring, the secondary burr thus results in the functional region of the bevel gear 10. In mass production, the primary deburring is therefore carried out in most cases from the inside to the outside, as symbolized in FIG. 1A by the block arrow P1.
A corresponding example is shown in FIG. 1A. A primary burr primarily occurs at the tooth edge 11.r of the concave flank, since this flank generally forms a relatively acute angle δ with the rear face 17 of the bevel gear tooth 10. If only the primary burr 20 were removed at this tooth edge 11.r (for example, by using a brush), a very sharp tooth edge 11.r would remain standing. Therefore, a chamfer is usually created at least in the region of the tooth edge 11.r by chamfering.
The situation after the chamfering of the tooth edge 11.r is shown in FIG. 1B on the basis of the bevel gear 10 of FIG. 1A. The profile of the first chamfer 12 can be schematically seen in FIG. 1B. As can be seen in FIG. 1B, a secondary burr 21 can form along the first chamfer 12.
However, a secondary burr does not always occur. Relationships have been shown here, for example, with respect to the quality of the cutting edges of the deburring tool. As long as the deburring tool has sharp cutting edges, the primary deburring runs relatively reliably. As cutting edges become blunter, the material of the bevel gear is no longer cut, but rather displaced. In this case, the tendency toward forming a secondary burr increases. Since the tooth edge typically does not have a linear profile between bevel gear teeth and, for example, the base of the bevel gear, the thickness of the chips to be removed during the chamfering varies. Also for this reason, secondary burrs can sometimes result.
Such a secondary burr 21 does not always occur and can also only form, for example, in a partial region of the first chamfer 12, as indicated in FIG. 1B.
Such a secondary burr 21 is accompanied by multiple disadvantages. On the one hand, a risk of injury during manual handling of such a bevel gear 10 exists because of the secondary burr 21. On the other hand, the secondary burr 21 can result in undesired soiling of the hardening device in which the bevel gear 10 is hardened. This is a disadvantage above all if the hardening is carried out in a closed hardening device, the interior of which is to be kept free of soiling as much as possible. If the tooth flanks are to be ground in the scope of fine machining, a secondary burr which was not removed can thus destroy the grinding tool. In addition, residues of a secondary burr can detach during installation in a transmission and result in problems therein.
Secondary burrs can be removed, for example, by the use of nylon or brass brushes, these tools are subject to wear, however. They therefore have to be replaced from time to time. To avoid the occurrence of secondary burr, the cutting edges of the deburring tools could also be reground more often, which is linked to a time and cost expenditure, however, especially because one has to intervene early enough, before secondary burr can begin to form at all.